This could be caused by a variety of factors, such as a network issue or a problem with your Kodi configuration.
To disable the message, you can go to Kodi's settings, click on "System" > "[definition=12,8][definition=12,9]logging[/definition][/definition]" > "Notifications", and then disable the "Show notifications" option. This will prevent Kodi from displaying any notifications, including the "Start failed - remote communication server" message.